Remove termios2 ioctl defintions from public headers

Remove termios2 ioctl defintions from public headers

The use of the termios2 ioctl interface is an implementation detail which
should not bleed into public headers.  Remove the PowerPC version of
<bits/ioctls.h> and define the termios2 ioctl numbers in <termios_arch.h>
instead.  Also remove the include check from there which is unneeded in an
internal header.